There are of course numerous types of heat exchangers that are used for a variety of purposes; e.g., to produce a cooling or heating effect or to improve efficiencies in heating or cooling systems by making the maximum utilization of available energy. Some heat exchangers, such as liquid heat exchangers, are relatively efficient. On the other hand, air-to-air type heat exchangers have been generally inefficient, and the energy savings usually did not justify the cost of the heat exchanger.
Air exhaust systems are becoming increasingly used to exhaust from an enclosure air that is undesirable because of temperature, humidity or pollutants. For example, the air in livestock confinement buildings must be exhausted because of the toxic gases that are created in such buildings. Unless exhausted, the air becomes warm and stagnant and the odor becomes almost over powering. The long-term health effects are not known, but it is believed that unless the air from such confinement buildings is frequently exhausted, farmers may suffer ill-effects, and the effect on the confined livestock is also not desirable.
More recently, concern has been publicized regarding radon gas in residential structures. One method of reducing the level of the harmful radon gas in living structures is to exhaust the air from the portion of the structure below ground level, this being the area of the structure where the radon gas invades the structure.
Regardless of the reason for exhausting air from an enclosed structure, the loss of energy can be fairly substantial especially during times of temperature extremes. Moreover, it is not only beneficial to exhaust undesirable air from an enclosed structure, but the air should be replaced with fresh air from outside the structure. Obviously, during times when the temperature of the outside air is much higher or lower then the temperature of the air within the structure, energy inefficiencies result.
Although air-to-air heat exchangers are known, they have had a number of problems and are relatively expensive for the energy savings produced. For example, fin-type exchangers are commonly used because of their higher efficiency. But if the air flowing through the exchanger contains a considerable amount of dust or other pollutants, the heat exchanger of the fin type can become rapidly clogged, thereby reducing its efficiency. Also, efficient distribution of the incoming outside air within the enclosed structure has not been satisfactory with prior art systems.
There is therefore a need for an efficient air-to-air heat exchanger that can be manufactured and installed at a relatively low cost and one which can be operated easily and with little or no maintenance.